1. Field of the Invention
This invention relates to an apparatus for trimming three-dimensional workpieces made of plastic or other materials, comprising a bottom platen for supporting the workpiece and a cutter, which is movable relative to the bottom platen along a line of cut.
2. Description of the Prior Art
Three-dimensional workpieces made of plastic, fiber-reinforced material, rubber or composite material, are used in various industries, for instance, as covering parts and instrument panel parts in vehicles. When said workpieces have been molded they must be trimmed so that they will have neat edges and specified dimensions. But the properties of the materials employed and the three-dimensional shape of the required lines of cut have previously given rise to substantial difficulties in the trimming of such three-dimensional workpieces. A knife used for trimming must still be operated by hand and this is unsatisfactory in industrial operations because of the high labor cost and of the inaccuracy involved. On the other hand, an automatic trimming can be performed by means of a water jet or laser because only weak cutting forces will be exerted on the workpiece in such trimming operations and it will be sufficient to support the workpiece in that it is simply placed on a suitably designed bottom platen. By means of the water jet or laser beam, that edge portion by which the three-dimensional workpiece protrudes over that edge of the bottom platen which extends along the line of cut can be severed without a need for an additional support so that the desired trimming will be achieved in that the cutter is simply moved along the predetermined line of cut. On the other hand, water jet cutting will require a rather complicated water-collecting system and involves a nozzle wear so that the operation involves high costs and a frequent servicing and noise must also be tolerated. In laser cutting the laser is accommodated in the cutter so that complicated means for directing the laser beam will be required. Besides, the high temperatures will result in changes of the material of the workpiece on the cut surface and the burning of the material of the workpiece during the cutting operation may result in a production of a gas, which is deleterious to health.